The question was migrated because the specific question of "How do I tell if my Thermistors are 10k or 100k?" is going to be best answered by users of Electrical Engineering SE. This also provides the SE network with more appropriate traffic based on the question at hand.
However, if the question of "How can I change the thermistors settings in Marlin firmware?" were to arise, then the question would be best suited here on 3D Printing. It might help both SE sites by providing links to each other's relevant questions for future users to reference.
If the question was something like "How can I wire a hotend?", this would be more appropriate here on 3D Printing SE as users in Electrical Engineering SE may not know as much about the topic compared to users in 3D Printing. This may be a poor example, but the idea is that there is strict correlation between hotends and 3D printing, whereas identifying thermistors is not a specific topic to just 3D printing.
After reading a few posts on SE meta, this one leads me to agree with you that this particular question may not have needed to be migrated. However, it exposes an important question of how we want to proceed with questions like this in the future? How far down the rabbit hole do we want to allow this site to go in this topic? I'd recommend others pitch in recommendations in answers here on what would be the appropriate topic in this case that can be applied to our On-Topic page so that it may be amended.